All of your repairs and remodeling cost would be added to your cost basis of the airbnb. No expenses or depreciation would be taken until you begin advertising and are ready to serve customers. This rule is the same whether you report income and expenses on schedule C or E.
One addition note; Be aware that if switching to a schedule C business, your profits over $400 will be taxed with an additional 15.3% SE tax. One advantage though is the airbnb "may" qualify for 15 yr recovery period and sec179 or Special Depreciation Allowance. If not, you would use 39 yr instead of 27.5 as in a rental.
